To me the English 'v'
sounds almost exactly like 'f' and I have trouble differentiating
between 'f', 'v' and 'w' when I (try to) speak English.

It never ceases to amaze me how subtle differences can be so important to native speakers of a language and yet sail by the ears of others without registering.  You're right, 'f' and 'v' are completely distinct in English, and we would never confuse words like "fine" and "vine".   And yet as an English speaker I have all kinds of trouble with the Icelandic/Norse vowels 'e' vs. 'ei', which I'm sure to you are totally distinct.

Tim